Many methods of applying liquid binding material to the back side of fabrics are known in the art. For example, U.S. Pat. No. 4,016,831 teaches applying foam backing to a fabric without the introduction of hose and streak marks on the fabric. A foam pillow is established on a fabric by confining it on two sides with guide plates, and on the front with a doctor blade or stationary rollers. The fabric is started moving, whereby the pillow is caused to generally roll or rotate about a generally horizontal axis. A gap of predetermined size between the bottom of the doctor blade or roller and the top surface of the fabric allows only a portion of the foam from the pillow to adhere to the fabric and be carried along therewith, the foam providing a backing for the fabric. The volume of foam in the pillow is maintained by the introduction of new foam into the volume of the pillow to at least two points on either side of the pillow, to flow generally along the axis of rotation of the pillow.
In another typical method of applying foam backing to a fabric, foam is applied to the upper surface of a moving fabric across the width of the fabric. The fabric, with the foam on its upper surface, then moves underneath an inflexible nip roll which extends across the entire width of the moving fabric and which is positioned a uniform distance above the upper surface of the moving fabric. The extent of this distance will determine the thickness of the foam backing on the moving carpet. After the moving fabric passes under the nip roll, it then travels to a drying oven.
The above-described method has proved to be satisfactory for applying foam backing to a carpet. It has been discovered, however, that problems occur when latex backing is substituted for foam backing in the above method. The use of the nip roll produces ripples in the fabric backing. Furthermore, after a period of time, the latex tends to dry and accumulate on the nip roll. This directly affects the amount of latex that can be applied to the fabric; moreover, the fabric backing tends to be uneven in thickness. It becomes necessary, in order to put a sufficient amount of latex down on the fabric, to pass the fabric by the latex applicator twice. Alternatively, the operator may choose to periodically close down the line to clean off the nip roll. Both alternatives are very time-consuming and, ultimately, very costly.
It would be desirable therefore, to be able to convert, with a minimum of effort, a standard foam application apparatus to utilize latex without any of the problems described above.